1. Field of the Invention
The present invention relates to a development apparatus, and an image formation apparatus such as a copying machine, a printer, and a facsimile apparatus that forms an image using the development apparatus.
2. Description of the Related Art
Conventionally, a development apparatus that develops an image with toner that hops on a surface of a toner supporting object, such as a toner conveyance substrate, is known wherein toner adsorbed by a developing roller or a magnetic carrier is not used.
For example, Patent Reference 1 discloses a development apparatus that includes a cylindrical toner supporting object that includes two or more electrodes arranged at a predetermined pitch in a circumferential direction. There, two adjacent electrodes constitute a pair, and electrode pairs are repeatedly arranged. Between two electrodes of an electrode pair, an alternating current (AC) electric field is formed. Then, the toner on one electrode of the pair is floated (hops) and lands on the other electrode, and vice versa. With a rotational drive of the cylindrical toner supporting object, the toner, which repeats hopping, is conveyed to a development position. At the development position, the toner that hops to the vicinity of a latent image on a latent image supporting object is pulled to the latent image by the electric field, and adheres to the latent image without descending toward the electrode of the toner supporting object. With this configuration, the toner that is hopping is used instead of the toner that is adsorbed by the developing roller, the magnetic carrier, etc. In this way, a low voltage development that cannot be realized with a conventional 1-component development method or a 2-component development method is realized. For example, the toner can be selectively adhered at a low voltage such as dozens V between an image part and a non-image part.
[Patent Reference 1] JPA H3-21967
[Disclosure of Invention]
[Objective of Invention]
According to the development apparatus disclosed by Patent Reference 1, by rotationally driving the toner supporting object, the toner that is supported on the surface of the cylindrical toner supporting object is conveyed to a position where a roller made from urethane foam is contacted so that the thickness of the toner on the surface of the toner supporting object may be regulated. However, since the roller made from the urethane foam is easily deformed when contacting an object, it is difficult to make the thickness of the toner uniform on the surface of the toner supporting object. Further, since the central section in an axial direction of the toner supporting object that is not supported by a bearing tends to sag, the thickness of the toner tends to be greater at the central section in a direction perpendicular to a surface moving direction of the surface of the toner supporting object than both ends. For this reason, according to the development apparatus of Patent Reference 1, the toner thickness tends to be uneven, and, therefore, development concentration tends to be uneven.